In my first post, I talked about attacking a smaller partner. When applying a technique, however, we are encouraged to go slowly in order to give time to the other student to first get used to the technique and allow their joints to get some stretch before tapping when they have enough. When I apply a shihonage, I also release my grip on my partner's wrist when I take them down, so their joint can readjust and I can finish without torturing them. And this is regardless of the size of the partner. One of the big guys in our dojo, one of those who can really show me wether I've mastered the technique or not, is very stiff and taps very early. Unbalancing him is difficult, but once the technique has worked, we need to handle him very delicately.
That's the beauty of Aikido: it really shows you how far your toughness goes.